Is there any employment based on only html .....?

Answer 1

soo I hav to learn CSS and js for efficient use of html right

Answer 2

Not likely because HTML without CSS would only make a default-style static webpage and without JS you could only have links to other pages and maybe some forms that get handled on server side with no client side validation or processing.

Only being able to use HTML limits the usefulness of the web pages too much, and would be a pretty ineffective developer.